\begin{subanswer}{rmergetwodataframes}
\begin{minted}{r}
df3 <- merge(df1, df2, by="colname")

df3 <- merge(df1, df2,
             by.x="x_colname",
             by.y="y_colname",
             all.x=TRUE,
             all.y=TRUE)
\end{minted}
The second statement will perform a full outer join.
Merging data frames are a very important part of data cleaning.
Make sure you can do it in all the languages you use, as well as SQL.
\end{subanswer}
